An ignition lead is a high voltage cable (typically 2–25 kV) used to deliver high voltage ignition pulses from an ignition system to some type of ignition device, which in turn uses the ignition pulses to generate sparks for igniting a fuel/air mixture. Due to the high voltage involved, electrical contacts of the ignition lead are susceptible to damage and often wear out before the other ignition lead components. Two such contacts are the terminal contacts located at each end of the ignition lead, one of which is a first terminal contact connecting a component of the ignition system, such as an exciter circuit, to the insulated center wire of the ignition lead, and the other of which is a second terminal contact connecting the center wire to an ignition device, such as a spark plug or igniter. With many ignition lead designs, if either of these terminal contacts become worn out, a time consuming and costly maintenance procedure is required to replace them.
Conventional ignition lead terminal contacts are not replaceable. Thus, when the contact wears out, the entire terminal assembly, or worse yet, the entire ignition lead may need to be replaced. This is particularly costly in applications having ignition leads of great length, sometimes exceeding twenty-five feet or more. Moreover, the time required by a skilled mechanic to replace an entire ignition lead, particularly in a gas turbine application, can be as much as four hours in some instances.
Replaceable terminal contact assemblies for ignition leads are known in the art, an example of which is built by Champion Aerospace Inc. of Liberty, S.C., for ARP670 type 2f termination. This replaceable contact assembly 10 is shown in FIG. 1 and generally includes a contact body 12 and a replaceable tubular connector 14. Contact body 12 is a generally cylindrical metallic component having a blind hole 20 extending into an upper axial end and a threaded male portion 22 extending from a lower axial end. The blind hole is designed to permanently receive the stranded center wire 24 of the ignition lead by crimping the contact body around the wire and firmly retaining it in place (as demonstrated by the illustrated deformation of contact body 12). The exterior threads of male portion 22 are threaded into replaceable tubular connector 14, which generally includes a longitudinal bore 30 having a threaded female portion 32 located at its upper axial end and an opening 34 located at its lower axial end. The threads of male portion 22 are sized to fit those of female portion 32 such that the replaceable tubular connector 14 can be threadingly attached and removed from the permanently attached contact body 12. Opening 34 is sized to receive an electrode of an igniter such that the high voltage pulse passing through contact assembly 10 is transmitted to the igniter. Other components, such as an insulator 36 and various connection pieces, are also seen in the drawing and are well known in the art. According to this design, when the terminal contact needs replacement, the tubular connector 14 is simply unthreaded from the contact body and a new connector is installed.
It is a general object of the invention to provide a replaceable contact assembly that can be used not only for ARP670 type 2f termination, but also for a wide variety of other types of ignition lead termination including, for example, other ARP670 termination designs.